$50M Mosman Property Smashes Record

Barely two months after a house in Mosman LGA broke the North Shore property price record, a new $50M has done it again. 

By Rita Bratovich

A sprawling three-story Mosman property with views across to North and South heads and down to Balmoral Beach, sold for an unprecedented $50 million in October last year and has smashed the North Shore property record.

The luxury home at 3 Kirkoswald Avenue was designed by esteemed Sydney architect, Susan Rothwell. It was purchased by the Balnaves philanthropic family in 2001 for what now seems like a bargain price of $6,525,000. 

During their tenure, Diane and Neil Balnaves had the home significantly renovated with input by architect, Rothwell. The 2235 square-metre block is situated on the prestigious cliff-top locale known as the “golden triangle” bordered by Burran Ave, Hopetoun Ave, and Kirkoswald St. 

The Palladian-inspired residence offers six bedrooms and seven bathrooms, centred around a striking atrium with a water feature. The elevated parcel affords the home sweeping views across Sydney Harbour and out through the heads to the ocean. Interior living spaces flow seamlessly to harbour-facing terraces overlooking a 20-metre infinity pool and spa, framed by gardens designed by Will Dangar.

Additional features include a gym, extensive wine cellar, butler’s pantry, steam room, automated gates and private au pair accommodation with separate access, alongside multiple Jetmaster fireplaces and travertine bathrooms appointed with Zucchetti tapware.

The Kirkoswald St mansion was sold by local prestige agents, Michael Coombs and Adrian Bridges of Atlas Lower North Shore. The identity of the new owner/s has not been disclosed but is rumoured to be an Aussie expat who is coming home. 

The previous record for the North Shore was held for only two months by a house on McLean Crescent (separated from the “golden triangle” by Rosherville Reserve). It sold in August 2025 for $43.5 million. 

The 1035 square metre block was purchased in 2010 for $5.5 million — a tidy profit. 

Both the McLean Crescent and Kirkoswald Street houses were sold off-market. It shows that buyers are not only willing to pay premium prices for homes in the area, but that there are hungry potential buyers just waiting for properties to become available.